Here is a summary of the top-line replica set configuration fields:
| Directive | Data Type | Notes |
| _id | String | Replica set name; corresponds to the replication.replSetName parameter in the mongod.conf file. |
| version | Integer | Represents a value designed to increment as the replica set is revised |
| protocolVersion | Number | As of MongoDB version 4.0, the protocol version must be set to 1 (default). This setting is in place so that future enhancements to the replication process can be made backward-compatible. |
| writeConcernMajorityJournalDefault | Boolean | The default value of true instructs MongoDB to acknowledge the write operation after a majority of replica set members have written a write request to their respective journals. All replica set members need to have journaling active if this value is set to true. However, if any member uses the in-memory storage engine, the value must be set to false. |
| configsvr | Boolean | If this replica set is used... |
